Technical Abstract:
Fifteen Holstein dairy cows were monitored for expression of adhesion molecules on lymphocytes in blood and milk at parturition and at intervals up to 21 days post partum. Using flow cytometric analysis, we examined expression of CD62L, CD11a, CD44, and alpha4/beta7 on T (CD4+, CD8+, gamma/delta+) and B lymphocytes. CD62L was expressed on 20-70% of T cell subsets in blood and 35-80% in milk from normal cows. CD62L expression on B cells was 20-25% in blood and 60-80% in milk. CD11a was found on 10-25% of T cells in blood and 35-70% in milk. CD11a was found on 10-15% of B cells in blood and 45-75% in milk. Alpha4/beta7 was expressed on 5-10% of T cells in blood and 10-35% in milk. Alpha4/beta7 was expressed on 5-10% of B cells in blood and 20-40% in milk. CD44 was found on 5-15% of T cells in blood and 20-55% in milk. CD44 was found on 5-10% of B cells in blood and 30-55% in milk. There were consistently more adhesion molecules, at a statistically significant level, on milk lymphocytes compared with blood lymphocytes. These differences may reflect increased recruitment of lymphocytes into the bovine mammary gland, which could then modulate the inflammatory response to pathogens during infection. Since CD62L and alpha4/beta7 are peripheral and mucosal homing receptors, respectively, these data suggest increased recruitment of both pools of lymphocytes into the bovine mammary gland.